That is simply a
hover effect. Go:
Admin Panel > Display > Pictures & Colors > Colors > CSS Stylesheet and add the below in your CSS:
- Code:
.frm-buttons{transition:all 800ms ease 0!important;}
.frm-buttons:hover{background:#000!important;transition:all 800ms ease 0!important;}
Edit: I just realized that the code i send was for the buttons and not for those you want! hehe sorry!
For your buttons, because you have images you need to add an other image as soon as you hover them. Due to that you need to make black images like the blue ones you have now so we can add them as hover effect!